Engine Coolant Temperature (ECT) Sensor Inspection
WARNING: This page is about a different car, the 2011 Suzuki SX4. However, it is still accessible from the selected car via links, so may be relevant.
Reference: ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL AND INSTALLATION
Immerse temperature sensing part of ECT sensor in water (or ice) and measure resistance between sensor terminals while heating water gradually.
If measured resistance doesn't show such characteristic as shown, replace ECT sensor.